Techniques have now been developed in the laboratory for the large-scale purification of C1q, C4, C3, 5, 6, 7, 8, 9, and the C57 complex. New assays have been developed for the C3b inactivator and for the protein Beta1H and the role of these proteins in C3b inactivation has been further explored. Studies are ongoing on the characteristics of this interaction which leads to the destruction of the opsonically active C3b site on erythrocyte surfaces. Studies have also been conducted on the interaction of complement with bacteria and considerable progress has been made in studies of the role of complement in producing the clinical symptoms of infectious disease.